Two fitness titans are on a path to square off in court, because David Beckham has sued Mark Wahlberg's company over a fitness deal that made the former soccer star way lighter in the wallet.

Beckham's company, DB Ventures Ltd, alleges in the lawsuit F45 "duped" him into signing on with F45 Training, a company in which Wahlberg has a 36% interest. M.W. also serves as the company's chief brand officer.

Beckham, who got close to Mark when he moved to Cali to play for the L.A. Galaxy, became F45's Global Ambassador. The selling point -- David has millions of social media followers, so it would presumably greatly expand the reach of the company.

Well, things didn't work out. Beckham says he never got the $10 mil he was promised ... this after the company's stock tanked. BTW ... those posts have been deleted.

F45 asked the judge to 86 the lawsuit, calling it "fraudulent," but the judge said the case will move on.

BTW ... David's not alone. Terrell Owens filed the same type of suit against F45 way back in 2017, claiming the company stiffed him to the tune of $700,000.